Secret Server has supported a "Mobile Edition" for over a year now but it is always tricky making sure that it works correctly on all devices.
Our approach was to bake mobile support into the base product (ASP.NET based) so it simply scales down to the capability of the device. That sounds simple but unfortunately it depends on making sure that functionality will work with all the limitations of various devices.
My own favorite BlackBerry 8820 does a reasonable job of helping me get to the password I need in emergencies but it is hardly a pleasant browsing experience. In fairness, no browsing on the device is particularly pleasant since it is slow, struggles with most layouts and has a small screen. That said, I love it dearly and browsing has never been a core requirement for me since email, contacts and calendar are definitely my most essential.
Today we had a customer ask about the Treo 700 so I tried out the emulator from the Palm website. It seems to work fine with Secret Server and I was able to browse around and access passwords.